Currently, one can mail a letter or a package through the U.S. Postal Service (hereafter referred to as USPS) using a postage indicium. In using a postage indicium, the sender usually uses a postage meter certified by the USPS (or the government postal service for other countries) to issue a postage indicium according to the weight of the mailpiece, the destination, and the chosen service. The meter will print on the indicium the paid postage amount, the indicium issuance date, location, the meter number, and a postal service symbol. The indicium also carries encryption information, which includes the postage amount and other postal data that relate to the mailpiece and the postage meter that prints the indicium. The encrypted information, which is in usually referred to as a digital token or a digital signature, is used for authentication purposes. The encryption is also used to protect the integrity of information, including the postage amount, imprinted on the mailpiece for later verification of postage payment. Since the digital token incorporates encrypted information relating to evidencing of postage payment, altering the printed information in an indicium is detectable by standard verification procedures. Examples of systems that are capable of generating and printing such indicia are described in U.S. Pat. Nos. 4,725,718, 4,757,537, 4,775,246 and 4,873,645, each assigned to the assignee of the present invention.
It is preferable to include in the indicium a plurality of alphanumerical characters, which can be read by an Optical Character Recognition (OCR) device and by an operator. The use of such OCR characters on an indicium has the combined advantage of human readability and machine readability. Currently, postage indicia and OCR characters can be printed by the sender using an inkjet printer, a thermal transfer print head or another personal printer. The print head of an inkjet printer typically has one or more rows of nozzles to simultaneously push out a plurality of ink droplets to form a corresponding number of rows of pixels. Under normal circumstances, when the velocity of the mailpiece relative to the print head is constant, the print head can produce row after row of pixels on the mailpiece in a rectangular matrix formation, with each row being substantially perpendicular to the traveling direction of the mailpiece, and the pitch between pixel rows also being constant. If the velocity of the mailpiece is not constant, the pitch between the pixel rows may vary. Under unusual circumstances, the pixel rows may be caused to become skewed in one direction or another. Consequently, the image produced by the printer may become distorted. For example, a vertical line may become angled, and a rectangle may be printed as a non-orthogonal quadrilateral.
An OCR reader usually uses a linear optical scanning device to scan in the printed image. An OCR engine uses some sort of-pattern matching algorithm to interpret the scanned-in image. If the OCR character region in an indicium is distorted when it is printed or when it is captured by the OCR reader, there is a possibility that the characters in that region may not be interpreted correctly. It is, therefore, desirable and advantageous to provide a method for improving the capture of an OCR character and/or other symbology region in an indicium on a mailpiece, so that the distortion in the OCR character and/or other symbology region can be detected to ensure that the symbols or OCR characters, as scanned in by optical scanner, are interpreted correctly.